Migrants from Honduras and El Salvador gathered on Oct. 25, 2018, near a park in Tecun Uman, Guatemala, waiting to cross from Guatemala to Mexico.
Nick Oza, azcentral.com

Several hundred Central American migrants walking on the road near Ciudad Hidalgo in southern Mexico after crossing the river from Guatemala are loaded onto buses and escorted by Mexican federal police and immigration officers on Oct. 26, 2018. It’s unclear if they were being taken to be deported or processed for asylum.(Photo: Nick Oza/The Republic)

"We are looking at every possible way within the legal construct that we have to make sure that those who do not have a legal right to come to this country, do not come in," Nielsen said. "So everything is on the table."

The reports follow intense scrutiny of the latest U.S.-bound migrant caravan, which has grown to 10,000 people, according to organizers in Mexico. It's still several weeks away from reaching the border, but it has prompted intense criticism from the Trump administration and the president himself.

Trump even threatened to send an additional 800 troops to the border in response. On Friday, Nielsen confirmed they had submitted a request for support to the Department of Defense, although she said that she didn't have information about the number of troops that would be authorized.

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As of Oct. 27, Ernesto Martinez, 27, and his wife Yesenia, 23, have been traveling with their three daughters, including a baby who was just 17 days old when they joined the caravan. Nick Oza/The Republic

Ernesto Martinez, 27, and his wife Yesenia, 23, are traveling with their three daughters, including a baby who was just 17 days old when they joined the caravan last Oct. 20. The family is from San Martin, Retalhuleu, Guatemala. They have pushed the baby in a stroller over 180 miles crossing through the state of Chiapas, before reaching the state of Oaxaca on Oct. 27 Nick Oza/The Republic

Ernesto Martinez, 27, and his wife Yesenia, 23, are traveling with their three daughters, including a baby who was just 17 days old when they joined the caravan on Oct. 20. They have pushed the baby in a stroller over 180 miles crossing through the state of Chiapas, before reaching the state of Oaxaca on Oct. 27, along with their two other daughters, 4-year-old Lynsi, and 6-year-old, Natalie. The baby, Reychel, turned 24 days old on Saturday. The family is from San Martin, Retalhuleu, Guatemala. Nick Oza/The Republic

Thousands of migrants from Honduras and other Central American countries traveling in a caravan reached the state of Oaxaca on Oct. 27, after crossing through the entire state of Chiapas on their way to the U.S. border. Nick Oza/The Republic

Bathing in the river offers a little relief from a day of walking in the oppressive heat for some of the thousands of migrants in the caravan. Thousands of migrants from Honduras and other Central American countries traveling in a caravan reached the state of Oaxaca on Oct. 27, after crossing through the entire state of Chiapas on their way to the U.S. border. Nick Oza/The Republic

Thousands of migrants from Honduras and other Central American countries traveling in a caravan reached the state of Oaxaca on Oct. 27, after crossing through the entire state of Chiapas on their way to the U.S. border. Nick Oza/The Republic

Thousands of migrants from Honduras and other Central American countries traveling in a caravan reached the state of Oaxaca on Oct. 27, after crossing through the entire state of Chiapas on their way to the U.S. border. Nick Oza/The Republic

Thousands of migrants from Honduras and other Central American countries traveling in a caravan reached the state of Oaxaca on Oct. 27, after crossing through the entire state of Chiapas on their way to the U.S. border. Nick Oza/The Republic

Several hundred Central American migrants walking on the road near Ciudad Hidalgo in southern Mexico after crossing the river from Guatemala are loaded onto buses and escorted by Mexican federal police and immigration officers on Oct. 26, 2018. It’s unclear if they were being taken to be deported or processed for asylum. Nick Oza/The Republic

Several hundred Central American migrants walking on the road near Ciudad Hidalgo in southern Mexico after crossing the river from Guatemala are loaded onto buses and escorted by Mexican federal police and immigration officers on Oct. 26, 2018. It’s unclear if they were being taken to be deported or processed for asylum. Nick Oza/The Republic

Several hundred migrants from Honduras and El Salvador gather near a park in Tecun Uman, Guatemala. They wait to cross the Suchiate River that divides Guatemala and Mexico in hopes of heading north to the United States. Under pressure from the United States, Mexico shut a bridge in an effort to halt the migrants, mostly Hondurans, from crossing the border into Mexico. Nick Oza/The Republic

Several hundred migrants from Honduras and El Salvador gather near a park in Tecun Uman, Guatemala. They wait to cross the Suchiate River that divides Guatemala and Mexico in hopes of heading north to the United States. Under pressure from the United States, Mexico shut a bridge in an effort to halt the migrants, mostly Hondurans, from crossing the border into Mexico. Nick Oza/The Republic

Several hundred migrants from Honduras and El Salvador gather near a park in Tecun Uman, Guatemala. They wait to cross the Suchiate River that divides Guatemala and Mexico in hopes of heading north to the United States. Under pressure from the United States, Mexico shut a bridge in an effort to halt the migrants, mostly Hondurans, from crossing the border into Mexico. Nick Oza/The Republic

Penely Suzet Steward, from Honduras, says she wants to go to the U.S. to visit her sick children. Steward is among several hundred migrants from Central America gathered near a park in Tecun Uman, Guatemala. They wait to cross the Suchiate River that divides Guatemala and Mexico in hopes of heading north to the United States. Nick Oza/The Republic

Penely Suzet Steward, from Honduras, says she wants to go to the U.S. to visit her sick children. Steward is among several hundred migrants from Central America gathered near a park in Tecun Uman, Guatemala. They wait to cross the Suchiate River that divides Guatemala and Mexico in hopes of heading north to the United States. Nick Oza/The Republic

Penely Suzet Steward, from Honduras, says she wants to go to the U.S. to visit her sick children. Steward is among several hundred migrants from Central America gathered near a park in Tecun Uman, Guatemala. They wait to cross the Suchiate River that divides Guatemala and Mexico in hopes of heading north to the United States. Nick Oza/The Republic

Migrants from Honduras and El Salvador gather near a park in Tecun Uman, Guatemala, on Oct. 25, 2018, as they wait to cross from Guatemala to Mexico and then head north to the United States. Nick Oza/The Republic

Migrants from Honduras and El Salvador gather near a park in Tecun Uman, Guatemala, on Oct. 25, 2018, as they wait to cross from Guatemala to Mexico and then head north to the United States. Nick Oza/The Republic

Migrants from Honduras and El Salvador gather near a park in Tecun Uman, Guatemala, on Oct. 25, 2018, as they wait to cross from Guatemala to Mexico and then head north to the United States. Nick Oza/The Republic

Migrants from Honduras and El Salvador gather near a park in Tecun Uman, Guatemala, on Oct. 25, 2018, as they wait to cross from Guatemala to Mexico and then head north to the United States. Nick Oza/The Republic

Migrants from Honduras and El Salvador gather near a park in Tecun Uman, Guatemala, on Oct. 25, 2018, as they wait to cross from Guatemala to Mexico and then head north to the United States. Nick Oza/The Republic

Migrants from Honduras and El Salvador gather near a park in Tecun Uman, Guatemala, on Oct. 25, 2018, as they wait to cross from Guatemala to Mexico and then head north to the United States. Nick Oza/The Republic

Migrants from Honduras and El Salvador gather near a park in Tecun Uman, Guatemala, on Oct. 25, 2018, as they wait to cross from Guatemala to Mexico and then head north to the United States. Nick Oza/The Republic

Migrants from Honduras and El Salvador gather near a park in Tecun Uman, Guatemala, on Oct. 25, 2018, as they wait to cross from Guatemala to Mexico and then head north to the United States. Nick Oza/The Republic

Migrants from Honduras and El Salvador gather near a park in Tecun Uman, Guatemala, on Oct. 25, 2018, as they wait to cross from Guatemala to Mexico and then head north to the United States. Nick Oza/The Republic

Migrants from Honduras and El Salvador gather near a park in Tecun Uman, Guatemala, on Oct. 25, 2018, as they wait to cross from Guatemala to Mexico and then head north to the United States. Nick Oza/The Republic

Migrants from Honduras and El Salvador gather near a park in Tecun Uman, Guatemala, on Oct. 25, 2018, as they wait to cross from Guatemala to Mexico and then head north to the United States. Nick Oza/The Republic

Migrants from Honduras and El Salvador gather near a park in Tecun Uman, Guatemala, on Oct. 25, 2018, as they wait to cross from Guatemala to Mexico and then head north to the United States. Nick Oza/The Republic

Migrants from Honduras and El Salvador gather near a park in Tecun Uman, Guatemala, on Oct. 25, 2018, as they wait to cross from Guatemala to Mexico and then head north to the United States. Nick Oza/The Republic

Pedro Castillo, 23 years old, from Honduras, took a raft from Guatemala to cross the Suchiate River to Mexico. Castillo is planning to join the migrant caravan. Mexican immigration officers ask Castillo for his identification. Nick Oza/The Republic

Nielsen said their request is for "engineering support and logistical support," but offered few other details, such as where along the border they would be deployed.

There are currently 2,100 National Guard troops stationed along the Southwest borderlands. But they are in secondary or supporting roles, so they have little to no interaction with migrants.

As the migrant caravan continued advancing through Mexico, still roughly 1,000 miles away, the DHS secretary said they continue working with the Mexican government to have some of them process their asylum claims there, instead of continuing up north.

"In the days to come, we will be making announcements on additional measures that we are looking at within our legal construct to ensure that this is an orderly process and that those who have no right to be in our country are able to be apprehended quickly," she said.

Trump's wall being built?

Nielsen's visit to Calexico marked the end of construction for one of four replacement projects along the U.S.-Mexico border. Starting in February, crews began to replace over 2 miles of aging, landing-mat steel barriers with 30-foot-tall bollard fencing.

But even though this project was identified as a priority and funded under the administration of President Barack Obama, Trump has repeatedly taken credit for it, stating at numerous rallies and appearances that construction of his border wall was under way.

Friday morning, as Nielsen arrived to the site of the newly-completed fence, just west of the Calexico border crossing, two men welded a engraved plaque to one of the bollards. It read: “This plaque was installed on October 26, 2018 to commemorate the completion of the first section of President Trump’s border wall.”

When asked whether the replacement fencing should be considered a wall, Nielsen said yes, adding that it should be though of as part of a "wall system" that includes technology, roads and boots on the ground.

"Looking at this, I would not attempt to climb it. Our hope is that it does just that. It serves as that impedance to prevent a flow over," she said. "It's a wall. This is what the president has asked us to do. It's part of the system."

U.S. Customs and Border Protection has three other ongoing projects to replace aging barriers with new 18-feet tall bollards. They're currently replacing 14 miles of fencing in San Diego, 20 miles in Santa Teresa, New Mexico, and four miles in El Paso.

Nielsen said Friday that they would also begin work next year to replace 11 miles of aging fencing east of the port of Calexico with 30-foot tall bollards.

Earlier this month, DHS waived a series of environmental laws in order to begin construction of 16 miles of new roads and barriers in South Texas.